The Aggressor ideology arose among the Home Clans during the post-Wars of Reaving era, partly as a reaction to the Bastion philosophy espoused by the Home Clans' leadership. Extant by 3090, the Aggressors were mostly found within the younger generations of Clan warriors. Citing the philosophies of Star Adder Khan Hannibal Banacek and selected writings of IlKhanBrett Andrews, the Aggressors believed that the best means of protecting the Clans from the Inner Sphere's taint was simply to annihilate it at the very source. As such, the Aggressors clamored for a new invasion of the Inner Sphere using the most violent measures possible.

In a similar manner to invade the Inner Sphere, the Crusaders believed that the only way to restore the Star League through Terra was by conquest. By doing this, they believed that would be achieving the goal of Kerensky's Hidden Hope Doctrine. The Crusaders also believed that this would be the only way to save the Inner Sphere from itself. In contrast, the Aggressors want to invade the Inner Sphere, but as a way to destroy the powers rather than subjugate them.

Because such methods would involve abandoning Clan honor rules completely, the leaders of the Home Clans prevented known Aggressors from gaining any authority, though the movement grew within those generations of warriors who had not experienced the extreme violence of the Wars of Reaving.

As of 3090, the Aggressors' strongest proponents were to be found within Clan Star Adder,[1] and the Ka'an and Josian Cloisters of Clan Cloud Cobra.[2] The Adder leadership sought to placate the Aggressors' thirst for combat by authorizing raids against the Escorpion Imperio and the Hanseatic League.

The status of the Aggressor ideology as of 3145, or even if it still exists, is presently unknown.